Prior art development environments used scripting languages to control the flow of an application. The languages contained individual code constructs called subroutines. Usually, a caller would call a subroutine to perform a certain task, and then receive a return code from the subroutine indicating its result. The caller would then execute a conditional branch instruction conditioned on the return code.
Accordingly, a developer who used subroutines needed to be familiar with all possible return codes that were output by the subroutines. Moreover, the developer needed to design a lengthy branch statement that accounted for all possible returns. Thus, the developer needed to be intimately familiar with the parameters and possible results of the subroutines.
In order to reduce the burden on the developer, prior art development environments had reusable subroutines that performed certain frequently-needed tasks. However, to increase reuse, these subroutines needed to allow for the different conditions that occurred in different calling situations. Therefore, the reusable subroutines had to be parameterized. That is, parameters had to be passed to the subroutine to tell it how to react to different situations. As reusable subroutines grew in complexity, more and more parameters became required. Since the developer had to be familiar with each possible parameter, even reusable subroutines created a heavy burden. In addition, if the application program interface (API) of a reusable subroutine changed, the developer had the burden of locating and changing all of the existing calls to that subroutine.
More recent prior art development environments were graphical in nature. Such graphical development environments used icons to represent various language components. Developers would draw lines or arrows connecting these icons. These lines defined a program flow (call flow). In the prior art, the burden of icon line connection was placed on the developer. Thus, the mechanics of line drawings as well as familiarity with each icon's functionality were burdens to developing successful program flow. For example, icons that behaved as a loop would have different line behaviors than icons that behaved as a branch.
Furthermore, prior art graphical development environments represented a subroutine as an icon in a call flow having a single input line and a single output line, even if the subroutine had multiple return codes. Therefore, the developer still had to be familiar with each possible return code and had to provide a mechanism for dealing with each one.
Prior art non-graphical development environments provided a way to create complex user-defined subroutines without too many parameters: overwritable subroutines. A subroutine can be thought of as containing its various functionalities. Some of these functionalities are always present, others are modified by parameters, and still others can be overwritten by the caller. Prior art non-graphical development environments allowed these overwritable functionalities to be represented as additional subroutines with default functionality defined and invoked by the containing subroutines. The caller of the containing subroutines could replace the default functionality of an overwritable subroutine by providing a corresponding overwriting subroutine. Obviously, the overwritable and overwriting subroutines each shared the same parameters and return codes.
However, the usefulness of overwritable subroutines in prior art was hampered by several limitations. In particular: (1) a lack of graphical representation of overwritable and overwriting subroutines; (2) an overwriting subroutine could only use data that was passed through the pre-defined parameter list--an extreme barrier to extending the default behavior; and (3) overwriting subroutines could only be defined once, not once for each call to the containing subroutine.
Accordingly, there is a need in the art for a graphical development environment that automatically connects icons in accordance with the call flow functionality of the underlying language component.
There is also a need in the art for a graphical development environment that graphically displays subroutines having multiple returns in a manner that eases the burden on the developer.
There is also a need in the art for a graphical development environment which tracks changes in subroutine APIs, so that those changes can automatically be reflected in all calls already made to that subroutine.
There is a further need in the art for a graphical development environment that graphically represents overwritable subroutines and improves their usefulness by enhancing their capabilities.